Propeller.



P. E. FERRERO.

P'ROPELLER- N FILED PROPELLER.

To all whom it may concern:

Be it knownthat 1, PAUL E. FERRERO, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in Propellers, of which the following is a specification.

Thisinvention relates to screw propellers, and particularly to those "of the disk type having a'variable pitch.

It has for its object the provision-of a propeller in which the ratio of the pitch of the leading face to that of thetrailing face of each blade is constant, regardless of the diameter or pitches selected.

It has for a futher' object the provision of a propeller in which the front, central, and

rear portions of each blade have curvatures bearing definite relations to each other and. which occupy definite proportions ofthe blade.-

It has for a further object the provision of a propeller in which the fluid acted upon receives at the leading edge only a slight acceleration from that of feed, this acceleration being increased at the rear part of the blade. p

A further obj ect is to provide the rear portion of each blade with a considerable rake which, in combination with fixed areas and curvatures, tends to overcome the centrifugal action of the water and cause the water to leave the propeller in lines parallel to\ the axis, or, if the rake is suflicient, to converge'in lines toward a point on the axis of the propeller rearwardly extended.

With these objects in view, the invention -is set forth in the accompanying drawings,

in which,-

Figure 1 is an elevation ofthe propeller, looking toward the working face;

Fig. 2 is a side elevation of the propeller; and i T Fig. 3 is a perspective view from the rear.

As'shown in the drawings, A'represents a two-bladed disk-propeller with blades mounted on a hub B having leadin edges 1, 1 and trailing edges 2,- 2. The leading edges 1 have a forward rake of 15, as shown, while the trailing edges have a rearward rake of'30. Each blade comprises a leading portion a, 0;, central portion 12, and a trailing portion a. In each blade the leading portion a occupies about one quarter'of Specification of Letters Patent.

' pendicular.

PAUL E. FERREBO, or PITTSBURGH, PENNSYLVANIA.

" Patented Mar, 6, 1917.

Application filed September 17', 1915. Serial No. 51,167.

the blade, the central portion 5 one quarter, I

of each blade is slightly convex (as viewed from the rear),'the central portion b is sub stantially fiat, and the trailing portion 0 is considerably concave. The curvature of portion a is twice that of portion a. The blade has a forward rake of 15 at the leading edge 1, which rake varies from 15 to 0 at the point where portion a joins portion Z), which has no rake at all, being per- I From the rear part of\portion b to the trailing edge of the blade, the rake Referring to Fig.-

varies from 0 to a 30 rearward rake at edge 2. i

As regards its operation, propeller 'is' designed to combine features which cause itto work according to certain well-defined pellers is'du'e largely to the fact that the .(the speed 0 the water entering the propeller with respect to the same) and grady propeller blades may be cast or ually increases its velocity up to the velocity of discharge with a corresponding gradation of recoil on the blade face, then the loss of work is the least possible and the lim t of efiiciency is reached, other things bemg equal. I have found that this result may be i very properly effected by giving the leading face a, a slight convex curve, the central face I) a flat face with a small uniform pitch near the hub, and the trailing'face 0 a concave curve which is twice that of the leading face a. This ratio is maintained 1n all blades, regardless of pitch. ,The diameter and pitch used will, of course, vary w th the conditions of the service required.

It is also known that screw propellers with variable pitches tend to accelerate and rotate the water, and that all propellers tend to throw ofi water by centrifugal action. To counteract this action, while maintaining theabove-mentionedadvantages of a gaining pitch screw, I give the leading edge a a forward rake of 15, the central portion is shock and vibration.

which the area of the propell perpendicular, and the rear portion a, because ofits greater curvature, is given a rearward rake -of These rakes, in combination with a blade area that in no radius is in excess of that of the water engaged, are designed to counteract the centrifugal tendency of the Water, and to derive .from it the maximum of recoil with the minimum of 1. A variable pitch screw propeller in which the area. of the propeller is substantially equal to the area of the column of Water engaged, the pitch of the leading face bearing a constant curve and surface ratio less than unityto that of the trailing face,

the curvature of the leading face being reversed to that of the trailing face.

2. A variable pitch screw (ll propeller in is substan tially equal to the area of the column of water engaged, and in the blades of which the pitch of the trailing face is twice that of the leading face, the curvature of the lead- :iEng face being reverse to that of the trailing ace.

3. A disk screw propeller in which the area of the propeller is substantially equal to the area of'the column of water engaged, the pitch of the leading face of each blade being one-half that of the trailing face, the curvature of the leading face being reverse to that of the trailing face.

4. In a screw propeller, a hub, blades mounted uponsaid hub, the area of said blades being equal substantially to that of the column of water engaged, each blade having a leading face portion slightly convex with respect to the Water engaged, and the leading edge having a" forward rake of 15, a'central face portion substantially fiat and perpendicular, and a trailing face portion with a concave curvature raked at an angle rearwardly of 30 at the trailing edge, the ratio of the pitch of the trailing face to that of the leading face being two to one.

In testimony whereof I aflix my signature.

' PAUL E. FERRERQ. 

